You need a combination of low HLB and high HLB emulsifyer. It all depends on your oil phase. Cetearyl Alcohol, Cetyl Alcohol, Tocopherol are also part of your oil phase. Or just use polymers. You won't need to calculate anything, just find a compatible one with % of your oil phase.

What the "high level" you are seeking to emulsify would be the relevant information here. As Perry informs, the polar nature of your oil load would dictate the chemical composition of your emulsifiers, based on the tried & true HLB system. However, as ngarayeva infers, should you have a really high level, then use a polymeric emulsifier such as Pemulen TR-2. That can accommodate up to 40% w/w as long as your formula has no electrolytes. As always mentioned here, put in the lab time and experiment.